1. Field of the Invention
The present invention relates to a control apparatus for a hybrid vehicle. In particular, the invention relates to a control apparatus for a hybrid vehicle that can improve fuel consumption by cutting off the cylinders (i.e., by closing both intake valves and exhaust valves of an engine) under certain conditions.
2. Description of the Related Art
Heretofore there is known a hybrid vehicle incorporating a motor in addition to an engine as drive sources for vehicle propulsion. One type of such a hybrid vehicle is a parallel hybrid vehicle where the drive output from the engine is assisted by the motor.
In the parallel hybrid vehicle, at the time of acceleration the drive output from the engine is assisted by means of the motor, while at the time of deceleration, various control is carried out such as performing battery charging by deceleration regeneration, so that the remaining charge (electrical energy) of the battery can be maintained while satisfying the requirements of the driver. Furthermore, since the structural mechanism is such that the engine and the motor are arranged in series, the structure can be simplified, and the weight of the whole system can be lightened. Therefore, there is an advantage in that there is a high degree of freedom in vehicle assembly.
Here, for the aforementioned parallel hybrid vehicle, there is a construction in which a clutch is incorporated between the engine and motor (for example, refer to Japanese Unexamined Patent Application, First Publication No. 2000-97068) in order to avoid the influence of engine friction (engine braking) at the time of deceleration regeneration, or the engine, motor and transmission are connected in series (for example, refer to Japanese Unexamined Patent Application, First Publication No. 2000-125405) in order to achieve maximum simplification.
However, in the former construction in which a clutch is installed between the engine and motor, there are disadvantages in that the construction is complicated by the clutch installation and the degree of freedom in vehicle assembly is worsened, and in addition the transmission efficiency of the power transmission system even when running is reduced due to usage of the clutch. On the other hand, in the latter construction in which the engine, motor and transmission are connected in series, since the amount of regeneration is reduced by the aforementioned engine friction, the electrical energy that could be conserved by regeneration is reduced. Therefore, there is a problem in that the amount of driving assistance (assistance amount) and the like by the motor is limited.
Furthermore, for a method of reducing engine friction during deceleration in the former type, there is a method for increasing the amount of regeneration by controlling the throttle valve opening at the time of deceleration using an electronic throttle control system to greatly reduce pumping losses. However, since a large amount of fresh air flows as is into the exhaust system during deceleration, it reduces the temperature of a catalyst and an A/F (air-fuel ratio) sensor, and there is a problem in that optimum exhaust gas control is affected detrimentally.
Therefore, the present invention provides a hybrid vehicle control apparatus that can achieve a significant improvement in fuel consumption, using motor driving assistance, by reducing the amount of engine friction through performing a reliable cylinder cut-off operation, and can also cut off the cylinders in an optimal state, so that the cylinder cut-off can be quickly cancelled in a case where it is not desirable.
The present invention is control apparatus for a hybrid vehicle with an engine (for example, engine E in the embodiment) capable of cutting off cylinders and a motor (for example, motor M in the embodiment) as drive sources of the vehicle, which performs regenerative braking by the motor depending on a deceleration state when the vehicle is decelerating, comprising: a cylinder cut-off determination section (for example, the processing associated with an all cylinder cut-off standby flag F_ALCSSTB in the embodiment) which determines whether the cylinders should be cut off depending on the running conditions of the vehicle; a cylinder cut-off cancellation determination section (for example, the processing associated with an all cylinder cut-off cancellation condition satisfied flag F_ALCSSTP in the embodiment) which determines whether the cylinder cut-off should be cancelled, depending on the running conditions of the vehicle while the operation of the cylinders of the engine is cut off; a cylinder cut-off execution section (for example, the processing associated with an all cylinder cut-off solenoid flag F_ALCSSOL in the embodiment) which operates an actuator (for example, a spool valve SV in the embodiment) for cutting off the cylinder operation of the engine when cylinder cut-off is determined to be possible by the cylinder cut-off determination section; and a cylinder cut-off control section (for example, the processing associated with an all cylinder cut-off execution flag F_ALCS in the embodiment) which cuts off the cylinders of the engine based on the operating conditions of the cylinder cut-off determination section, the cylinder cut-off cancellation determination section and the cylinder cut-off execution section, wherein when a voltage (for example, voltage VB in the embodiment) of a drive source of the actuator that is operated by the cylinder cut-off execution section is greater than or equal to a predetermined voltage, and a temperature of a medium that acts by the operation of the actuator is within a predetermined range, the cylinder cut-off determination section determines that cylinder cut-off is possible.
With such a construction, it is possible to cut off the operation of the cylinders of the engine by the cylinder cut-off control section after cylinder cut-off is determined to be possible by the cylinder cut-off determination section and the actuator for cutting off the cylinders of the engine is instructed to operate by the cylinder cut-off execution section.
Furthermore, when the cylinder cut-off cancellation determination section judges the cancellation of cylinder cut-off while the operation of the cylinders is cut off, after the cylinder cut-off execution section cancels the operation of the actuator, it is possible for the cylinder cut-off control section to operate the engine normally.
Here, the cylinder cut-off determination section judges that cylinder cut-off is possible only in the case where the voltage of the drive source of the actuator and the temperature of the medium satisfy certain conditions, so that it is possible to prevent switching to cylinder cut-off operation in a case where the voltage of the drive source of the actuator or the temperature of the medium are not adequate. Accordingly, there is an effect of preventing a reduction in the response of the actuator, enabling reliable switching to cylinder cut-off operation.
In the present invention, the cylinder cut-off execution section may apply an oil pressure of a working fluid by operating the actuator, to close both an intake valve (for example, intake valve IV in the embodiment) and exhaust valve (for example, exhaust valve EV in the embodiment) of the engine, and the temperature of the medium may be the oil temperature (for example, oil temperature TOIL in the embodiment) of the working fluid.
With such a construction, the oil temperature of the working fluid is maintained within a predetermined range, adequate actuator response is ensured, and cylinder cut-off can be performed. Therefore, there is an effect that both the intake valve and exhaust valve can be closed reliably.
In the present invention, when an inlet negative pressure (for example, inlet pipe negative pressure PBGA in the embodiment) of an inlet pipe is greater than or equal to a predetermined value that is on the atmospheric pressure side, the cylinder cut-off determination section may determine that cylinder cut-off is possible.
With such a construction, since cylinder cut-off can be performed at a time of low engine load when the inlet pipe negative pressure is greater than or equal to a predetermined value that is on the atmospheric pressure side, it is not necessary to cut off the cylinders at a time of high engine load when cylinder cut-off is not required.
In the present invention, the cylinder cut-off cancellation determination section may determine that cylinder cut-off cancellation is possible when the oil pressure (for example, engine oil pressure POIL in the embodiment) of the working fluid is less than or equal to a predetermined pressure.
With such a construction, there is an effect of preventing operational failure of the actuator in the case where the oil pressure of the working fluid becomes less than or equal to a predetermined pressure, enabling switching to normal operation.
In the present invention, the cylinder cut-off cancellation determination section may determine that cylinder cut-off cancellation is possible when the remaining charge of a battery (for example, battery 3 in the embodiment) that drives the motor is outside of a predetermined range.
This construction prevents failures occurring through being unable to ensure sufficient energy for motor assistance at the time of returning to normal operation in the case where the remaining charge of the battery is outside of a predetermined range, that is, in the case where the remaining charge of the battery is too low. Furthermore, extra regeneration is not required in the case where remaining charge of the battery is too high. Therefore, there is an advantage in energy management.
In the present invention, the cylinder cut-off cancellation determination section may determine that cylinder cut-off cancellation is possible when a gear ratio (for example, previous gear position NGR in the embodiment) is less than or equal to a predetermined value, that is on the low speed side.
With such a construction, there are effects in that regeneration in a region where regeneration efficiency is poor can be avoided, and it is possible to avoid the busy operation due to cylinder cut-off switching (that is, switching being performed frequently) in a low speed region.
In the present invention, the cylinder cut-off cancellation determination section may determine that cylinder cut-off cancellation is possible when the rate (for example, rate of change DNE in the embodiment) of change of the engine speed (for example, engine speed NE in the embodiment) is greater than or equal to a predetermined value.
With such a construction, there is an effect of preventing stalling the engine in the case where the rate of change of engine speed on the decreasing side is greater than or equal to a predetermined value, for example if sudden deceleration is performed to stop a vehicle, enabling switching to normal operation.
In the present invention, the cylinder cut-off cancellation determination section may determine that cylinder cut-off is possible when a clutch of a manual transmission vehicle is determined to be partially engaged.
With such a construction, there are effects of preventing the engine from stalling, for example in the case where the clutch is partially engaged in order to stop the vehicle, and preventing unnecessarily cutting off the cylinders if the gears are changed to accelerate, enabling switching to normal operation.
In the present invention, the cylinder cut-off determination section may determine that cylinder cut-off is possible when an outside air temperature is within a predetermined range. With such a construction, it is possible to prevent the engine from being unstable when all cylinder cut-off is performed.
In the present invention, the cylinder cut-off determination section may determine that cylinder cut-off is possible when a cooling water temperature is within a predetermined range. With such a construction, it is possible to prevent the engine from being unstable when all cylinder cut-off is performed.
In the present invention, the cylinder cut-off determination section may determine that cylinder cut-off is possible when atmospheric pressure is greater than or equal to a predetermined pressure. With such a construction, it is possible to prevent all cylinder cut-off being performed in a state where a sufficient level of the brake master power negative pressure cannot be ensured at the time of brake operation.
In the present invention, the cylinder cut-off cancellation determination section may determine that cylinder cut-off cancellation is possible when vehicle speed is outside of a predetermined range.
In the present invention, the cylinder cut-off cancellation determination section may determine that cylinder cut-off cancellation is possible when engine speed is outside of a predetermined range. With such a construction, in the case where the engine speed is low, it is possible to prevent low regeneration efficiency and the inability to ensure sufficient oil pressure for all cylinder cut-off switching. Also in the case where the engine speed is too high, it is possible to prevent the inability to perform cylinder cut-off switching because the oil pressure is too high due to high engine speed, and an excessive consumption of working fluid for cylinder cut-off.
In the present invention, the cylinder cut-off cancellation determination section may determine that cylinder cut-off cancellation is possible when brake master power internal negative pressure is greater than or equal to a predetermined value. With such a construction, in a case where sufficient brake master power internal negative pressure cannot be obtained, it is possible to prevent all cylinder cut-off from continuing.
In the present invention, the cylinder cut-off cancellation determination section may determine that cylinder cut-off cancellation is possible when a throttle is not fully closed. With such a construction, in the case where the throttle opens even a little from the fully closed throttle state, continuation of all cylinder cut-off is cancelled, thereby enhancing marketability of a vehicle.